Hello OFL :) I would like to address you of the thread in betta chat entitled Forum Snobs and watch out for any more rude comments and if you could possibly chime in to keep things under control... Thanks! :)

Toxic reports, look for aquarium and/or natural water ways reports/use opinions/experiences...etc.....Might be some scientific reports.....lots on different trees especially on forestry sites....Look for local government/forestry/habitat type site too....

Never hurts to try-but I would still only use naturally dried and fallen from the tree leaves-some species of green leaves can be toxic-I would google it and see what kind of info you can find.....
The one toxic tree you do want to avoid is the Black walnut due to the juglone...its more in the bark, nuts, nut husk, roots than leaves-but I wouldn't want to risk it....